Re: Inactive memory keep growing and how to release it?

[Simon Jeons]

On 03/14/2013 08:39 PM, Hillf Danton wrote:
> On Sat, Mar 9, 2013 at 10:14 AM, Will Huck <will.huckk@xxxxxxxxx> wrote:
> > Cc experts. Hugh, Johannes,
> >
> > On 03/04/2013 08:21 PM, Lenky Gao wrote:
> > > 2013/3/4 Zlatko Calusic <zlatko.calusic@xxxxxxxx>:
> > > > The drop_caches mechanism doesn't free dirty page cache pages. And your
> > > > bash
> > > > script is creating a lot of dirty pages. Run it like this and see if it
> > > > helps your case:
> > > >
> > > > sync; echo 3 > /proc/sys/vm/drop_caches
> > > Thanks for your advice.
> > >
> > > The inactive memory still cannot be reclaimed after i execute the sync
> > > command:
> > >
> > > # cat /proc/meminfo | grep Inactive\(file\);
> > > Inactive(file):   882824 kB
> > > # sync;
> > > # echo 3 > /proc/sys/vm/drop_caches
> > > # cat /proc/meminfo | grep Inactive\(file\);
> > > Inactive(file):   777664 kB
> > >
> > > I find these page becomes orphaned in this function, but do not understand
> > > why:
> > >
> > > /*
> > >    * If truncate cannot remove the fs-private metadata from the page, the
> > > page
> > >    * becomes orphaned.  It will be left on the LRU and may even be mapped
> > > into
> > >    * user pagetables if we're racing with filemap_fault().
> > >    *
> > >    * We need to bale out if page->mapping is no longer equal to the
> > > original
> > >    * mapping.  This happens a) when the VM reclaimed the page while we
> > > waited on
> > >    * its lock, b) when a concurrent invalidate_mapping_pages got there
> > > first and
> > >    * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
> > >    */
> > > static int
> > > truncate_complete_page(struct address_space *mapping, struct page *page)
> > > {
> > > ...
> > >
> > > My file system type is ext3, mounted with the opteion data=journal and
> > > it is easy to reproduce.
> Perhaps we have to consider page count for orphan page if it
> could be reproduced with mainline.

Why? /proc/sys/vm/drop_caches will call invalidate_mapping_pages() 
instead of truncate_complete_page().

> Hillf
> ---
> --- a/mm/vmscan.c	Sun Mar 10 13:36:26 2013
> +++ b/mm/vmscan.c	Thu Mar 14 20:29:40 2013
> @@ -315,14 +315,14 @@ out:
>   	return ret;
>   }
>
> -static inline int is_page_cache_freeable(struct page *page)
> +static inline int is_page_cache_freeable(struct page *page, int has_mapping)
>   {
>   	/*
>   	 * A freeable page cache page is referenced only by the caller
>   	 * that isolated the page, the page cache radix tree and
>   	 * optional buffer heads at page->private.
>   	 */
> -	return page_count(page) - page_has_private(page) == 2;
> +	return page_count(page) - page_has_private(page) == has_mapping + 1;
>   }

page count 2 is for page cache and isolator, why you check mapping 
separately?

>   static int may_write_to_queue(struct backing_dev_info *bdi,
> @@ -393,7 +393,7 @@ static pageout_t pageout(struct page *pa
>   	 * swap_backing_dev_info is bust: it doesn't reflect the
>   	 * congestion state of the swapdevs.  Easy to fix, if needed.
>   	 */
> -	if (!is_page_cache_freeable(page))
> +	if (!is_page_cache_freeable(page, mapping ? 1 : 0))
>   		return PAGE_KEEP;
>   	if (!mapping) {
>   		/*
> --
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@xxxxxxxxxx  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/